Jiggle Journey

A witch whose breasts grow every time she gets laid should be a self-motivated woman. She is not. She'd rather nap in a hammock than do the one thing that fuels her own superpower, so she's been packed off on a journey and you're the one who has to make sure it's jiggly enough to matter.

The setup is thin on plot beyond that: a witch, a road, a magic system built entirely around cause and effect below the neck. It's less a quest than an excuse to keep her moving from one encounter to the next.

You steer her through that journey, pushing toward encounters that feed the growth mechanic rather than around them, with some strategy and combat mixed in to keep it from being a straight click-through. Whether you play it as gradual escalation or go straight for the collapse-under-her-own-chest ending is your call.